Internet fail
Welcome to the internet, thanks for playing. You lost.
I'll assume you're not a complete troll and tell you why:
1. Unenforceability. To stop the dissemination of such knowledge (and it is knowledge that is dangerous here; once one person creates the theory, thousands more can implement it) you need to be able to take down web sites, FTP sites, Torrents, Usenet messages, and so on in any jurisdiction in the world. Possibly hosted on hacked computers, without the owners' knowledge. G'luck. (Oh, and by the way, the bad guys will be exchanging it on USB keys, under the table at the pub.)
2. Dual use. These tools have legitimate applications (password strength checks, lost password recovery). The tools that are out-and-out for criminal purposes (bank login harvesters, botnet tools, etc) are, surprise surprise, criminal. (But, oh wait, they're still out there... makes you wonder, doesn't it?)
3. Full disclosure. It's been found that, without the threat of a publically-available exploit, software companies *will not fix* their bugs. Microsoft has already switched to a more secure password hash (starting from Win2K) and admins who know how to configure their systems can laugh at this attack (as can those running Vista). Without things like l0phtcrack, this wouldn't have happened. We'd all be sitting ducks for those who are already ignoring the law.